The question for me who is better? Full comparison need to be run, and see where each of them have better and not performance. Everyone try to sell but without highlight the pros comparing to the available product on the market is not mean to much for me. It is mean spending of time to compare one new thing. While if the company want to really attract me fast they should directly point where are 100% better there there and there.

I really like the way that Atmel have merged the best features from the AVR and ARM families to generate this new offering. Of course they already have MCUs based on Cortex-M3 and -M4 processors (and higher), but these new Cortex-M0+ parts fill a real need with regard to miniscule power consumption required by the Internet of Things.
I particularly like their Event system, which allows peripheral to do things autonomously without waking the MCU unless it's necessary -- such as an A/D converter that periodically takes a reading but only wakes the MCU if the value falls inside (or outside) specified bounds...